In many cases, a blood filter device such as an arterial filter is incorporated in an artificial heart-lung circuit used for heart surgery involving extracorporeal circulation for the sake of safety. To provide security for patients, it has been demanded strongly that such a blood filter device be configured so that it can remove minute foreign substances in the artificial heart-lung circuit, thrombi formed during operation, or air that has entered or been released from the circuit, so as not to allow them to enter the patient body.
A filter generally used in the blood filter device is a polyester screen filter with pores of about 20 to 40 μm. The interior of the housing serves as a path for blood in order to eliminate dust, impurities, thrombi and the like when the blood passes through the filter. For example, Patent document 1 discloses a blood filter device as shown in FIGS. 21, 22.
FIG. 21 is a cross-sectional view showing a blood filter device. A housing 1 is made of resin for example, having a head portion 2 forming an upper structure, a filtration portion 3 forming a middle structure, and a bottom portion 4 forming a lower structure. The housing 1 has a lateral cross section of a circular shape.
A blood inlet 5 is provided at a lateral face of the head portion 2. On the top of the head portion 2, an air vent 6 for discharging air such as air bubbles is provided. The head portion 2 is formed so that the inner diameter is reduced gradually toward the top of the head portion 2. This allows air bubbles to be gathered to move upward along the inner peripheral face of the head portion 2. The head portion 2 has a lateral cross section of a circular shape, and is provided with the blood inlet 5 so as to allow blood flow horizontally into the head portion 2 and along the inner wall of the head portion 2. The blood that has flowed in from the blood inlet 5 flows downwards into the filtration portion 3.
The filtration portion 3 has a cylindrical shape in which a filter 8 for filtering foreign substances in blood is disposed. The filter 8 is disposed to partition a cavity of the housing 1 into the head portion 2 side and the bottom portion 4 side. A blood outlet 7 is provided at the bottom portion 4, and thus a liquid that has flowed into the head portion 2 from the blood inlet 5 passes through the filtration portion 3 and then flows out from the blood outlet 7.
As schematically shown in FIG. 22, the filter 8 is formed of a filter sheet 8a made of a sheet-like mesh material folded to form a plurality of pleats, where ridgelines 8b of the plural pleats are aligned in a plane to have an appearance of a flat plate. Namely, an envelope of the ridgeline 8b of respective pleats is flat. The filter 8 is disposed so that the flat surface traverses the cavity of the retaining portion inner cylinder 3a (filtration portion 3), namely, the ridgelines 8b of the pleats traverse the cavity of the filtration portion 3 in parallel to each other. The ridgelines 8b of the respective pleats are oriented in parallel to the direction of the blood inlet 5 or the blood outlet 7. As a result of disposing the ridgelines 8b of the respective pleats in parallel to the direction of either the blood inlet 5 or the blood outlet 7, air bubbles can be removed easily due to the blood or a priming solution flowing in parallel to the ridgelines 8b of the pleats.
As shown in FIG. 21, a bonding resin 9 is supplied into an outer peripheral part of the filter 8, and the filter 8 is bonded to the inner peripheral face of the filtration portion 3 with the bonding resin 9.
According to this configuration, foreign substances, thrombi and the like in blood can be removed reliably, and since there are no obstacles in the vertical direction of the filter 8, air bubbles adhered onto the top face of the filter 8 during a priming operation can be removed easily by merely applying a physical impact to the housing.
Patent document 1: WO2004/084974